To be exact 폭탄마냥 as in 폭탄마냥 보고 있다. But 폭탄 means bomb, so i assume it is probably some kind of idiom and not literally means bomb in that context?
I mentioned that 마냥 means 처럼; I will correct your example sentences as the following:
A. 왜 도시락을 폭탄처럼 보고 있지?
B. 작은 헛기침 소리 외엔 별다른 말을 하지 않는 의사를 인찬은 시한 폭탄처럼 보고 있었다. 언제 의사의 입에서 자신이 예상하는 말이 튀어나올지, 기다리는 심장이 두근거림을 참지 못하고 토해내고 있었다.
Sentence A literally means "Why (are you / is he / is she / are they / am I) seeing the lunch (box) as a bomb?" I do not know the background of your example, but it is good to know the history of Korea. This is a quotation from an article on The Korea Times:
The other is Yun Bong-gil who in 1932 staged an attack with a bomb disguised as a lunch box at a Japanese army celebration of Emperor Hirohito’s birthday in Shanghai, killing several high-ranking Japanese military figures.
Most Koreans living in Korea have heard about the lunch box bomb (도시락 폭탄), so this figure of speech is highly effective. Sentence A may not closely relate to the history nonetheless. Interpret the words considering the context.
Sentences in B indicate that 인찬 is looking at the doctor as if the doctor were a time bomb because the doctor is keeping silent. 인찬 is nervous because he thinks the doctor is going to say something big to him suddenly like a time bomb awaiting for the time. Now, use your imagination to understand this figure of speech.